Alkali metal compounds of substituted phenols are usually prepared by reacting the substituted phenol with the appropriate base. The substituted phenols react with strong bases to form salts called phenates.
Referring particularly to the preparation of sodium pentachlorophenate as an illustration, it is known to prepare this material by reacting molten pentachlorophenol at about 90.degree. C. with sodium hydroxide in water to form a solution having about 35 weight percent sodium pentachlorophenate based on the total weight of the aqueous reaction product. This solution is subsequently dried in a fluid bed dryer at high temperatures (200.degree. C.-280.degree. C.) and long residence times (average 4 hours) to yield the product in bead form. The conditions of drying promote the formation of toxic by-products which are undesirable in the product mix. Illustrated below are the undesirable reactions and by-products that occur during the drying conditions. ##STR1##
To date, present commercial practices for the preparation of sodium pentachlorophenate require that the reaction occur in the presence of water or a liquid reaction medium which must subsequently be removed. Dioxin formation is integrally associated with the heat history of the drying process. For use as an antimicrobial agent, it is also desirable and usually specified that the sodium pentachlorophenate contain not more than, and preferably less than, 1 ppm hexachlorodibenzo-p-dioxin and 30 ppm octachlorodibenzo-p-dioxin. Present facilities using a fluid bed dryer cannot routinely produce alkali metal phenates which meet desired dioxin specifications.
Industrial interest in economic production techniques and environmentally-safe products, fosters a continuing effort to frugally produce an antimicrobial substance, having the activity and water-solubility of an alkali metal phenate, such as sodium pentachlorophenate, without the toxic by-products.
In accordance with the present invention, an alkali metal phenate is obtained in an energy saving process and with little or no dioxin formation.